Home PYQs UPPSC UPPSC MCQs Prelims 2005 (GS Paper I)

Question

In cold weather, aquatic animals survive when water at the top layer of the lake freezes into ice because:

  1. they can breathe in ice
  2. they have enough of accumulated oxygen inside them
  3. their body structure is such that they can survive without oxygen
  4. water has highest density at 4°C so underneath the top layer of ice there is layer of water

Answer:

Option D: water has highest density at 4°C so underneath the top layer of ice there is layer of water

Detailed Solution:

The correct answer is “water has highest density at 4°C so underneath the top layer of ice there is layer of water”.

In cold weather, when the top layer of a lake freezes into ice, aquatic animals can survive underneath because water has its highest density at 4°C.

This means that as water cools down to 4°C, it becomes denser and sinks, while water below 4°C (up to the freezing point) becomes less dense and stays on top, eventually forming ice. This allows a layer of liquid water to remain beneath the ice, providing a habitat for aquatic life.